Injection molding is a process in which resin is injected under pressure into a closed mold having a shaped cavity. After the resin is injected, the mold is separated and the shaped plastic part is removed. Such a mold typically has a plurality of ports through which the resin is injected into the cavity, though in some instances only one port is used. The cavity may contain a fiber preform or fiber wound article with the injected resin infiltrating the fibers and subsequently cured to produce a part of fiber reinforced resin.
After the resin is injected into the preform and cured, it is preferred to remove the resin injection ports to break away the plastic which has cured inside the port. If not removed, the resin in the port may lock the part in the mold.
In U.S. Pat. No. 4,797,236, an injection molding method is disclosed, with an injection port shown located in a stationary plate 11. The port has a tapered inner passage which increases in diameter from the outer surface to the inner passages in the mold. The outer surface has no taper and no means are described or shown for removing the port from the mold.
Referring to FIG. 1, a port 1 is disposed in a mold 2 having upper and lower portions 3 and 4 which define a cavity 5. A channel 6 connects a port passage 7 to the cavity to deliver resin thereto. A fiber preform 8 is disposed in the cavity.
Using ports similar to that described above, problems arise in removing the port from the mold. Typically, bolts are used to fasten the injection port to the mold, and these must be removed to release the port. However, in many instances, even after the bolts are removed, the port may not be released as the cured resin is fairly tough and will not break easily. A slide hammer or other device may be required to break the plastic and release the port. When done in this manner, it is difficult to predict where the plastic will break. When not broken properly, the plastic may hinder removal of the cured part from the mold. Also, resin may infiltrate into the space between the port outer surface and the mold, locking the port in the mold and increasing the difficulty of removal.